You can ride for many miles on worn out bearings. As long as they're adjusted as well as possible and greased, they will keep rolling. The hub isn't going to seize up, start smoking, explode, or crack in half. It may make some noise.
I used to agonize over perfectly adjusted and smooth running hubs and bearings. Get them as good as you can and ride. We're talking about a bicycle. Make it fun not a chore.